This invention relates in general to copy prevention, and more specifically, to a web and process for using the web for preventing unauthorized copying.
Various approaches have been conceived for preventing the unauthorized copying of documents.
In an abstract entitled "No-Copy" Attachment For Copier, J. D. Harr et al, IBM Technical Disclosure Bulletin, Vol. 17, No. 11, Apr. l 1975, pp 3434 and 3435, a system is described in which a document having fluorescent material deposited in or on it that is invisible under normal lighting, fluoresces red under long wavelength ultraviolet radiation of the background areas of an original. The red radiation emitted during exposure to ultraviolet radiation is detected by suitable sensors which activate means to interrupt the functioning of a copier. In other words, detection of a response to illumination by ultraviolet radiation occurs in the wavelength domain. Since paper having an ordinary white appearance is preferred by most users and since ultraviolet light from artificial or natural lighting is normally present under ordinary ambient conditions, the presence of a red radiating material in paper may impart a nonwhite coloration to paper. Another disadvantage of this concept is that one can easily identify fluorescent material protected original documents by illumination with a simple blacklight. Moreover, since fluorescent materials that fluoresce in the blue color range are usually employed in paper to impart a whiter appearance to the paper in room light, fluorescent copy prevention materials that radiate blue would be unsuitable for the system described in the IBM Technical Disclosure Bulletin.
Fluorescent toners have also been suggested in Japanese Patent Publication No. 58-14842 to Tomoegawa Seishijiyo K.K., published Jan. 27, 1983. These toners fluoresce during copying so that the photoreceptor cannot distinguish the image areas from the non-image areas. Unfortunately, some fluorescent materials cannot readily be employed with standard light sources already in a copier because the light source emits wavelengths that do not encompass the wavelength needed to activate the fluorescent material and/or the photoreceptor is insensitive to the wavelengths emitted by the fluorescing toner. The required use of special toner compositions limits applicability of this concept to specific classes of machines specifically designed to handle such materials and may require trade-offs in copy quality over typical toners. The toner also appears to require specific exposure sources and photoreceptors for effective operation because it relies on the resulting image contrast between print and background regions to be small. Moreover, special toners of this type would also normally require replacement of the toner when the copier is to be used for making copyable documents.
In British patent publication No. 1,332,185, published Oct. 3, 1969, certain photochromic materials are suggested to render an original document uncopyable. However, like many fluorescent materials, some photochromic materials cannot readily be employed with standard light sources already in a copier because activation of the photochromic materials require light in a specific wavelength regime which may lie outside the wavelength of the exposure source already in the copier Furthermore, in modern flash illuminating copiers, the exposure time may be insufficiently long for the photochromic change to be functional. In addition, the technique again requires the image contrast between the print and the background regions to become sufficiently small to become unreadable. Also, the original once activated generally requires special treatment to recover its original condition within a reasonable time, a clear disadvantage.
Magnetic toners have also been suggested for incorporation into original documents to prevent copying. However, such use requires that an original be made xerographically and that a dedicated copier containing magnetic toner be utilized to form the uncopyable document. The copier used to form the magnetic images cannot readily be used to form copies with non-magnetic images because of the inconvenience of changing the toner from magnetic toner to non-magnetic toner and also because the design parameters of a xerographic engine utilizing magnetic toner are different in general from those for an engine utilizing nonmagnetic toner. Further, since magnetic toners are already widely used for conventional copying purposes, their use as a copy prevention marker for secure documents would tend to be precluded.
In an abstract entitled Unauthorized Copy Prevention, G. D. Bruce, IBM Technical Disclosure Bulletin, Vol. 18, No. 1, June 1975, p 59 and in U.S. Pat. No. 3,831,007 to J. P. Braun, a modulated image on the background areas of an original is detected by suitable sensors. However, the modulated image is visible and imparts to the document an unusual appearance different from ordinary paper.
In U.S. Pat. No. 3,713,861, an imaged document is coated, for example, with an overcoating which fluoresces in both the image areas and the background areas during the exposure step of an electrophotographic copying process to prevent image formation on a photoreceptor. The application of an additional overcoating involves an inconvenient extra processing step. Moreover, the coated paper is not aesthetically equivalent to ordinary paper.
Some copy prevention systems form distorted images. But, even in these systems that form copies bearing distorted images of the original images, the images formed are often still readable.
While systems utilizing the above-described known approaches may be suitable for their intended purposes, there continues to be a need for the development of an improved system for preventing unauthorized copying which avoids paper having an unusual appearance; components that are difficult or impossible to be installed by the owner or a technical representative at the site of a machine to be modified; costly hardware; easily detectable copy prevention webs; special photoreceptors or exposure lamps; machines having an anti copying capability that is difficult for the owner to turn off and the like.